Instrument for chemi- or bioluminescent analysis

ABSTRACT

The invention relates to an instrument for chemi- or bioluminescent analysis of the concentration of a constituent of a sample gas (G 1 ) which in a reaction chamber (C) reacts with a liquid reagent (R 1 ) in a luminescent manner. The liquid reagent (R 1 ) is ejected into the reaction chamber (C) by ejection means. The sample gas (G 1 ) can be used as propellant in the ejection means (E) sucking the liquid reagent (R 1 ) into the propellant and as an aerosol be sprayed into the reaction chamber. Carefully mixed with the sample gas, it generates chemiluminescent radiation (L 1 , L 2 ) in the field of view of a photodetector (D). The propellant (G 1 ) can also be prepared so that either heating or cooling occurs on expansion in the reaction chamber (C). By providing walls of the reaction chamber with reflecting layers, the main portion of the luminescent radiation reaches the detector (D).

TECHNICAL FIELD

This invention relates to an instrument for the generation and detectionof bio- or chemiluminescent radiation. This is achieved by bringingtogether in a reaction chamber two or more gaseous or liquid substancesinto the field of view of a photodetector means; at least two of thesesubstances yield luminescence upon reacting and at least one of them isa gas.

BACKGROUND ART

For the quantitative analysis of small amounts of gaseous substancesseveral methods are used at present, such as spectrophotometry,fluorimetry, gas-chromatography and galvanometry. All of these requirerelatively expensive equipment. Particularly in cases where an accuratedetermination of very small amounts of i.e. gaseous pollutants (withhygienic limits set at 1 ppm or lower) is required, the availableinstruments tend to be both costly and bulky. Due to a growing demandfor a better working environment, a need has long been felt forreliable, simple, cheap and in particular, sensitive measuring devicesfor the quantitative determination of gaseous or gasborne pollutantswith concentrations ranging from 10 ppm down to thousandths of ppm.

It is known (i.e. Anal. Chem., 45, 443A (1973)) that a large number ofgaseous substances can be accurately determined by means ofchemiluminescent reactions. Such reactions generate light, the intensityof which is directly proportional to the concentration of the reactingsubstances. If during the reaction the luminescent substance is inexcess, the light intensity is directly proportional to theconcentration of the substance investigated in the sample; thus a simplemeasurement of light intensity yields an accurate determination of thesample concentration. The radiation can be generated in any of thevisible, ultraviolet and infrared spectral regions.

Generally, a luminescent substance can be either a solid, a liquid or agas. When a gaseous sample reacts with a liquid reagent, the lightgeneration will be proportional to the area of the gas-liquid interface.

In a known device this is achieved by adsorbing the reagent on a gel andpassing the gaseous sample over the surface of the gel (Geophys. Res.65, 3975 (1960)). The disadvantage of this method (as that of otherdevices in which a gaseous sample is bubbled through a liquid reagent)is the relatively small size of the gas-liquid interface. When theobjective is to continuously determine a gaseous pollutant such asozone, continuous blowing of the sample against the reagent in the gelor bubbling it through the reagent causes the latter to successivelychange its concentration as a result of evaporation and reaction withthe sample, resulting in an unsatisfactory accuracy of the analysis.

If both reagent and sample are gaseous a number of known devices areavailable where both gases mix and react to yield chemiluminescence. Inthe British Pat. Nos. 1,341,346 and 1,353,722 two different reactionchambers are described, in which the gases are mixed in front of aphotomultiplier. These devices can only be used for purely gaseouscomponents.

In the American Pat. No. 3,998,592 a thermoelectric heat-pump is usedfor simultaneous heating of the reaction cell and cooling of thephotomultiplier. This device is also intended for gaseous componentsonly. Furthermore, the thermoelectric heat-pump only yields a certainpreset temperature difference between the hot and the cold side. As arule, the photomultiplier has to be cooled further--either directly orby extracting more heat from the hot side of the thermoelectricheat-pump. With some bio-or chemiluminescent systems better light yieldsare obtained at temperatures below ambient temperature; in such casesthe above-mentioned device is not applicable.

DISCLOSURE OF THE INVENTION

The present invention relates to an instrument for bio- orchemiluminescent analysis without the above-mentioned limitations and inwhich the concentration of a sample gas is measured in a reactionchamber in the field of view of a photodetector means, reacting in aluminescent manner with a liquid reagent from a reagent container. Saidinstrument comprises means for ejecting said liquid reagent into saidreaction chamber in the form of aerosol particles and means forproviding a flow of said sample gas to the reaction chamber at least atatmospheric pressure. By causing the sample gas flow to be pulsed witharbitrarily presettable pulse duration and intervals, two advantages aregained. On the one hand a higher sample gas pressure can be used,resulting in a considerably higher luminescent intensity and on theother hand, a lower consumption of the reagent occurs due to theintermittence. The ejector means may use the sample gas as a propellantin such a way that the liquid reagent via one or several pipes isarranged to be sucked into the propellant gas jet by the ejection effectand converted into an aerosol.

In some cases, an inert gas may serve as propellant. By choosing acarrier-gas with a high inversion temperature, such as N₂, the gas iscooled on expansion outside the ejector. If heating is desired instead,a carrier-gas with a low inversion temperature, such as H₂, can be used.

The ejector device is preferably arranged to be adjustable with respectto the size of the aerosol particles. The latter should of course be assmall as possible in order for the total gas-liquid interface to be aslarge as possible. A radius of 10⁻³ cm for the aerosol particles willgive a total surface of 3000 cm² for 1 cm³ of liquid. Adjustment can beachieved by the positioning of the ejector tube in the ejector nozzle.

It can also be advantageous to design the liquid reagent tube (tubes)entering the ejector (ejector tubes) in the form of capillaries, atleast in some part of the tube. In this way, the liquid substance willnow flow back beyond the capillary. The time needed for the carrier-gasto suck up liquid from the capillary to the ejector nozzle can be madeequal to the time needed for the carrier-gas to flush the reactionchamber and the detector window before the liquid reaches the ejectorand the start of the chemiluminescent reaction.

If the light generation in the reaction is weak, the light flux to thedetector can be increased by making the walls of the chamber reflecting.The detector is placed on the outside of the window or on a transparentpart of the reaction chamber.

In order to prolong the usage of the liquid reagent it is advantageousto drain the reagent back into the reagent container by means of anelectronically controlled valve. This is done as long as the detectordoes not yield a signal or if the signal has a lower amplitude than apreset threshold value. Otherwise the reagent is channelled into acontainer for consumed reagent. One advantage with said method is thatthe reproducibility is considerably increased due to the fact that onlyfresh reagent will participate in the luminescent reaction.

If substances occur whose detection is not required but which also yieldchemiluminescence with the particular reagent being used, thephotodetector unit may be arranged to contain two or more detectorelements each of which is supplied with a transmission filter fordifferent wavelengths or wavelength bands. The relation between thesignal amplitudes then decides whether the detection should result in analarm or not.

In some cases it can be advantageous to keep the detector (if arrangedwithin the reaction chamber) or the detector window, free of liquidsubstances. This can be achieved by means of a gas- or air curtain.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in more detail below with reference to theenclosed FIGS. 1-3. FIGS. 1 and 2 show an embodiment of the invention,of which FIG. 1 shows a block-diagram, while

FIG. 2 shows an intersection of an enlarged drawing of the reactionchamber with the ejector device. It also shows a photodetector meansmounted onto the reaction chamber.

FIG. 3 shows the front view of an ejector device with two ejector tubes.

In FIG. 1 a gaseous sample G₁ in the form of ambient air is arranged tobe sucked through a filter F by means of a pump P, which subsequentlycompresses the sample G₁ in a sample volume V. When a magnetic valve M₁opens, the sample (which in the present case is the propellant gas aswell) flows with high speed through a nozzle H surrounding an ejectiontube K (FIG. 2) in the ejector device E and in so doing sucks up liquidreagent R₁ from the reagent container S₁ by means of the ejector effect.The propellant gas G₁ thus draws the liquid reagent R₁ into the gas-jet,here consisting of ambient air. The reagent R₁ is dispersed and issprayed in the form of an aerosol into the reaction chamber C. The lightgenerated by luminescence partly falls directly L₁ (FIG. 2) onto thedetector unit D and partly on the reflecting walls. After having beenreflected one or more times L₂, the light reaches the detector D. Thewalls of the reaction chamber C are coated with a reflecting layer B.The major part of the reagent is led either through a magnetic valve M₂back to the reagent container S₁ or in cases when the measured lightexceeds a preset threshold value on the signal processing unit A, is ledto a container for waste reagent S₂. The result of the measurement ispresented by a display unit N. This measuring sequence is repeated aftera predetermined interval.

FIG. 2 shows the reaction chamber C with ejection means E and detectormeans D. The ejector tube K is adjustable along the length direction tominimize the drop size. The wall T onto which the detector means D isarranged is transparent for the radiation in question. Furthermore, thereaction chamber is provided with drain passages U and W for gas andliquid respectively.

FIG. 3 is a front view of a possible embodiment of an ejecting meansprovided with two ejector tubes K, one for reagent R₁ and one for gasG₂. One advantage of the embodiment of FIG. 3 is that, apart from beingused with liquid reagent R₁ it also can be used for gaseous reagent G₂.Provided an inert propellant gas G₁ is used, both a liquid reagent R₁and sample gas G₂ can be sucked through ejector tubes K. This rendersthe instrument very flexible. In the case where the propellant gas G₁sucks in another gas G₂ (eventually together with a liquid R₁) by meansof the ejector effect, said other gas G₂ can be samples of ambient air.

We claim:
 1. An apparatus for luminescent analysis of the concentrationof a constituent in a sample gas, comprising:a reaction chamber; meansfor ejecting into said chamber a quantity of liquid reagent in the formof aerosol liquid particles; means for providing a flow of sample gasinto said chamber at least at atmospheric pressure; means for detectingluminescent light produced by reaction of said sample gas with saidaerosol liquid particles; and means for collecting used liquid reagent.2. Apparatus according to claim 1, in which said means for providing aflow of sample gas to said reaction chamber is arranged to provide saidgas flow in pulses with predetermined duration and pressure. 3.Apparatus according to claim 1 or claim 2, in which said means forejecting uses the sample gas as a propellant.
 4. Apparatus according toclaim 2, in which said means for ejecting uses a gas mixture as apropellant gas with the sample gas as one of the components. 5.Apparatus according to claim 4, in which said sample gas is prepared toeither increase or decrease its temperature on expansion.
 6. Apparatusaccording to any one of claims 1, 2, 4, or 5, in which said means forejecting comprises means for adjusting the aerosol particle size. 7.Apparatus according to claim 1, in which the walls of said reactionchamber are made reflective to the luminescent light.
 8. Apparatusaccording to claim 1, in which said means for detecting comprises two ormore detector units, each provided with a transmission filter for adifferent wavelength or wavelength band, said detector units beingelectrically connected to a signal processing means.
 9. Apparatusaccording to claim 1, in which said means for collecting used liquidreagent is arranged to lead the used liquid reagent from said reactionchamber to a reagent container as long as the signal amplitude from saidmeans for detecting is lower than a predetermined value, and arranged tolead said used liquid reagent from said reaction chamber to a means forreceiving waste reagent liquid if the signal amplitude reaches orexceeds said predetermined value.
 10. A method of luminescent analysisof the concentration of a constituent in a sample gas, comprising thesteps of:providing a reaction chamber; ejecting into said chamber aquantity of liquid reagent, in the form of aerosol liquid particles;providing a flow of sample gas at least at atmospheric pressure intosaid chamber, whereby said aerosol liquid particles and said sample gasreact to produce luminescence; detecting said luminescence to determinethe concentration of the constituent; and collecting used liquidreagent.
 11. A method according to claim 10, wherein said flow of samplegas is provided in pulses with predetermined duration and pressure. 12.A method according to claims 10 or 11, in which said flow of sample gaspropels said aerosol liquid particles into said reaction chamber.
 13. Amethod according to claim 10, in which said sample gas is a constituentof a gas mixture and the flow of said mixture propels said aerosolliquid particles into said reaction chamber.
 14. A method according toclaim 13, in which said gas mixture is prepared to either increase ordecrease its temperature upon expansion.
 15. A method according to claim10, further comprising the step of adjusting the size of said aerosolliquid particles to optimize reaction with said sample gas.
 16. A methodaccording to claim 1, further comprising the steps of reflecting saidluminescence from the walls of said reaction chamber.
 17. A methodaccording to claim 1, further comprising the steps of filtering saidluminescence into separate wave length bands and separately detectingluminescence in each of said bands.
 18. A method according to claim 1,further comprising the steps of recycling said used liquid reagent whenthe concentration of the constituent is below a predetermined value anddisposing of said used reagent liquid when the concentration of theconstituents is above said predetermined value.